1. Field of the Invention
The present invention relates to a motor drive control system that carries out a motor drive control digitally by use of a PWM (Pulse Width Modulation) drive.
2. Related Background Art
In a digital speed control using a direct PWM drive of a motor, a PWM drive frequency signal may be generated by an oscillation circuit, e.g., an RC oscillation circuit using a resistance and a capacitor, thereby controlling the digital speed control non-synchronously with each set of switching timings of the motor.
In such a motor drive control system, however, the PWM drive pulse number of each phase and the time from the switching timing of each phase until the first PWM drive pulse are different from each other and deviation in the driving timings of each phase has occurred. As a result, rotational irregularity has occurred, particularly when a large PWM pulse number cannot be used for the switching timings of each phase by the stepping speed, and the loss, in a motor which has a large number of rotations, the the on-times of the respective PWM pulses are different from each other as the pulses are non-synchronous with each other, and the effects of the above-mentioned timing irregularity are increased whereby the rotational irregularity is also increased. Further, since the system uses a resistance and capacitor, a frequency variance has occurred due to manufacturing variances of the devices or elements, and the characteristic variance due to temperature.